This book in many ways rehashes some of his 'beefs' against leading edge physics - string theory, quantum mechanics, etc. but takes a bit of a new approach by making the bold claim that Time is itself the fundamental component of the structure of reality. As a result of this his claim is that the laws of physics must evolve and change over time. He also makes the claim that this 'setting of time as invariant' is another way of looking at Einstein's relativity (which set the speed of light as invariant - resulting in different experiences of time, time dilation, etc).

I personally have always wondered if what Einstein did was somewhat arbitrary (fixing the speed of light and that it was invariant) and have always wondered if other elements might not be set as invariant with the same results of giving us a completely new view of reality.

I found the book quite interesting. Lee Smolin is a bit of the 'bad boy' of physics but if you are interested in that perspective this is worth the read.